Device for measuring the speed of vehicles



pt 28,1931 J. M. WALTMAN Em 1,803 224 DEVICE FOR MEASURING THE SPEED OF VEHICLES Filed Nov. 13. 1928 2 Sheets-Sheet 1 April 28, 31. J. M. WALTMAN ET AL 1,303,224

DEVICE FOR MEASURING THE SPEED OF VEHICLES Filed Nov. 15, 192g 2 Sheets-Sheet 2,

Patented Apr. 28, 1931 UNITED STATES oEFicE .qo a t vns vrnarmuswnnrman, OETHE HA UE, AND JAN FRhIDIERIKSIRKS, or-

vooRscno'rEN, NETHERLANDS DEVIQE FOR MEASURING THE vem nesl Application fil ed November 13,1928, Serial No. a an i, s g iii Gerinany' llovember 18, 1927.

The present-invention relates to means for measuring the-spee'dof vehicles moving along a; straight path, particularly J the speed" of motor cars.

6 his of special advantage to-construct the improved device in such away that the deflecting means-consist of two prisms having a different refractive angle and'coveri'ngeach approximately half the cross section of the raysof the single telescopes. Furthermore .itisadvisable tofrender the deflecting means attachable-tothe oculars or the objectives of the double telescope so as tobe able to .also use the latter without the device, if neces- 15 sary. 1

As a length, which, with the different types of motor cars is substantially the same and therefore particularly suitable as a" basis for carrying out the measurement of the speed,

20 there comes in the firstplaceinto question the track, at dusk' preferably the distan'ceof the headlights. As the same lie-in the horizontal line it is suitable to providelthe double telescope with guides which admit of attaching the prisms insuch a way that, when using the device, the refrzictiveedges: are in ap proximately vertical position, the displacement of the image then being horizontal;

\Vhen using attachable Icelandspa'r splats and the like it is, of course, also. advisable to provide the device with a. corresponding} guiding appliance. 7

The object of the present invention. is to enable the improved deviceto: be applied to cost of the instrument andproviding one which is'suitedfor those who. arei accustomed touse one eye'only. v 1

According to this invention the retracting prisms are mounted on a changing device whereby they may be brought, in'succession,

in front of the objectiveof a monocular telea monocular telescope thus reducing the-total should-alwaysbe the same and the, refractiveindices or the prisms should'be chosen so that,"with a definite unit, of measurement,

( such as the wheel traclgof f a tattle the first observation (i. e. when -the sto'p watch will be started) will take place when the vehicle is at one" predetermined *point and the second observation (i; e. when'thestop watch will bestopp'ed) whenthe vehicle isat a second predetermined point at a convenient distance from the observer. however, that unit of measurement be changed, calculations become necessary, or, alternatively, prisms of different refractive indices must be employed. If, forexa'mple, it-is-desiredtouse the device forlichecking thel speed' of motor cars, it is inevitable that, if'the wheel-track gauge be adopted as the most suitable unit of measurement for observations day, a.

second unit of measurement must be taken for night observations and the 4 distance between the headlights may bettaken as the basis.

-:' In orderlto save calculations, a. second fpai-rv of. prisms can. be provided on the changing. dBVICG-SO that, alternatively, saidssecondrpalr. 7

canbe brlought in front of the objective, their effect being different from. that i of: the first pair, and! such that; the distancelimits" (.i. e. beginning and end) of the test will be the same forthe second unit of measurement. i :The device be particularly complete if the stopwatch beadapted to becoupled, in twopositionawith thechan ging device,

in such a manner that, on being set in one I posit on, it effects the changing of the one pair ofi'defiecting the other po i ion fiesta har n of the other pair. w

bodiments the invention are illustrated.

v In the 'accompanying drawings some em- 1 shojwsdiagrammatically in afplan view the, operation of the devicewhen in use,

the full lines indicatingv thereal position of a car, the dottedlines, however, indicating the :1

position effected by the deflection.

Fig. 2 shows the double image observed in thegright telescopeat the moment at which thecar is on the distance 112 whereas Fig. 3

shows the doubleimage, observedin the left telescope at the moment at which the car is on the distance M.

An embodiment'of the invention is illustrated in Fig. L as a diagrammatically median section and in Fig. 5 as a plan. To make the illustration clear,.the lever carrying the stop watch, in Fig. 4 is misplaced by as compared with the position shown in Fig. 5. Fig. 6 represents a modification of the device in perspective and-on a smaller scale.

How the measurement of speeds 1s carrled out may be seen from the followmg example.

On a straight road there is located an observer, who is provided with both a stop watch and a, telescope d to which the device is fitted,;the,r.efractive angle [12 of the prism .71 amounting to 39 (displacement of the image 3 1? 387') and the refractive angle a]. of the ,prism i --;to'l (displacement of the image If the-observer on the road be approached by a motor'car, whose'track a=1-,35 m. is known, the double images of the car wheels,

perceived by-the single telescope fitted with the prism itwill appear to be just displaced In the same way the measurementof the distance may be carried out on the car receding from the observer. Themeasurement of time withthe stop watclnwhich is set going at the period of the distance and stopped at the periodof the distance mfimay yield.

e s -1,, wherefrom resultsthe speedo of-the car according to the Equation 2;

When measuring the speed of an approachhour Y ing car the observer looks at first only through the right telescope till he observes M the image shown in Fig. 2. At this moment the movement of the 'stop' watch 1S started.

CIT

Thereupon he only looksthrough the. left telescope till he observes the image shown in' Fig. 3, at which moment the movement of the stopwatch is stopped. The speed' of the car can then be determined inthe manner already indicated. v

- In Figs. 4 and 5 the device is shown in position' on a monocular fieldglass cl and is'provided with a clamping ring 6 and clamping screw w, by means of which it can be attached to the mount y of the objective of the field glass d. The clamping ring I) is cast integrally with a disc 2 which is provided with a circular opening f coaxial with the clamping ring I). The disc 2 carries a pin 9 serving as a pivot for a rotatable disc h which is provided with four semicircular prisms 2' 2' 2' and 2' having the angles of refraction a1, 112,113 and a l. A spring 1, mounted on the disc 2 and provided with a catch pin 76 forms,

in conjunction with four corresponding depressions m ,m mtandm, in the rotatable disc h latching means for locating any one of the prisms 2' 2' 2' and-2' in the correct position, for the time being; in front'of the mount cl of the objective. A lever p which is also rotatable on the pivot g, ,is adaptedto be coupled with the rotatable disc h by means ofa leaf spring 0 and two pairs of lugs n and n situated at, 180 to one another. Hinged on this lever 39 is a watch casing g, serving to house a stop watch 1", the movement of which can bestartedand stopped by means of a switch knobs projecting from the casing g. In the position shown, the casnations are to be made of the speed of motor carsiapproaching the observer on a straight road and over a stretch beginning 130 and ending 30 metres away. The prisms i and i are-chosen for daylight measurement, with the wheel-track gauge as the unit of measurement; and the prisms 2' and 2' for measure- -ments in the dark, with the distance between the head lights as the unit. The angles of refractionv of' the prisms have been determined as follows, for certain kinds of'glass' and the usual length of measuring stretch a1=as' 30'! 1 3:26 30" I oz2=2 46 0 a4=1 54 30 For daylight measurement the spring 0 must be arranged between the lugs 01 sothat the stop watch lever 2? lies between the prisms i and 7?. The prism i is set in front of the mount d of the objective and the observation [of an approaching vehicle through the field glass a displays a dual image as above set forth. At the moment of passing the 130 111. limit, the displacement of the halves of the duel image corresponds with the'dimensions of' the -ywheel-track gauge. At this moment the observer starts the stopwatch 7- by pressingv the knobs, the pressure so exerted turning the casing g and the rotatable disch coupled thereto'through 90 about the pivot g, thereby bringing the prism 2' in front of the mount 'y oft-he objective. Owing to the value of thecalculated angle 0:2, the displacement of the image through a distance corresponding with the unit of measurement occurs at the second limit of distance, i. e. the

. vide 30 m. limit, and the watch 1' isstopped by pressing the knob s. The time indicated by the watch as consumed in travelling through the distance 130- 30 100 metres gives, when n'lultiplied by 10, the time taken by the car in travelling 1 kilometre.

For night work, with the distance between the headlights as the unit of measurement, the same procedure is followed, but the spring 0 must be located between the lugs n and, correspondingly, the prisms 2' and rinsed in place of the prisms 2' and 7?. Obviously, the changing device may be duplicated for binocular telescopes or a singlechanging device may carry eight prisms.

Since various motor car makers turn out their products with Wheel-track gauges and headlight spacing which diifer from the normal, it will be a convenient practice to prothe observer with a table from which, with the aid of the measured time, he can read off the speed of such cars without having to make calculations.

In contrast to the embodiment shown in in succession, in front of the objective ofthe telescope, the stop watch being connected with the changing device in such a manner that starting the stop watch can simultaneously effect the changing of the refracting prisms.

In testimony whereof we aflix our signatures. J OHANN ES MARTIN US WALTMAN. JAN FREDERIK SIRKS.

Figure 4, the stop watch 1" in the embodiment according to Figure 6 is fixed on to the casing 6 in which the prisms 2 4 are housed, whilst a lever u, projecting from the casing, is mounted on the rotatable disc and serves for changing the prisms. The drawing shows only one lever u, which is used for measuring in daylight. Diametrically opposite to this lever is a similar lever which takes the place of the lever u for measuring in the dark, this being accomplished by turning the rotatable disc through180". On the prism casing is a small spring-controlled slide a, by means of which the rotatable disc is fixed with the prisms for daylight and night observation.

What we claim is:

1. In an apparatus for measuringthe speed of vehicles moving in a straight line the combination of a telescope with two refracting prisms to be interposed within the path of the rays of the telescope and with a stop watch, the refracting prisms having a different refractive angle being adapted to cover each approximately half the cross section of the rays of the telescope, and a changing device on which the prisms and stop-watch are operatively mounted whereby they may be brought in succession in front of the objective of the telescope.

2. In an apparatus for measuring the speed of vehicles moving in a straight line the combination of a telescope with two refracting prisms to be interposed within the path of the rays of the telescope and with a stop watch, the refracting prisms having a difi'erent refractive angle, being adapted to cover each approximately half the cross section of the rays of the telescope, a changing device on which the prisms and the stop watch are operably mounted whereby they may be brought- 

